using System; using System.Text;

using System.Windows.Forms;

using System.Threading;

namespace WindowsApplication1

{  

   public partial class Form1 : Form

    {     

     public Form1()        

     {            

     InitializeComponent();     

    }

        private void button1_Click(object sender, EventArgs e)    

     {          

   Thread th = new Thread(YourThread);       

      th.Start();        

}

        private void textBox1_TextChanged(object sender, EventArgs e)   

      {      

       if (textBox1.Text.Length >= 4)       

      {         

        detailCollectedEvent.Set();                

      // 当textBox1的文本超过4位，发一个通知     

        }       

  }

        AutoResetEvent detailCollectedEvent = new AutoResetEvent(false);    

     void YourThread()  

       {           

  MessageBox.Show("input you bank account details into the textbox");           

  detailCollectedEvent.WaitOne();                  

    // 等候通知           

  MessageBox.Show("we will keep the secret.");

        }  

   }

}

线程暂停。